I am happy to announce that project ppcoin is now close to beta quality and will be released to public soon.

What are we announcing?

- First implementation of hybrid proof-of-work/proof-of-stake - Long term energy non-dependence (meaning if hashrate drops network is still protected) - Long term energy efficiency (assuming the continuation of Moore's law) - Proof-of-work mint rate is a function of difficulty (every 16x in difficulty mint rate is halved) - Proof-of-stake mint rate is less than 1% annually - Centrally broadcasted checkpoint for transaction settlement and defend against 51% attacks

- No premine - No tax - Open source - Same license term as Bitcoin to help advancing cryptocurrency technology

Schedule

- Beta release is tentatively scheduled for Aug 19, 2012. In the first release only command-line client is available (ppcoind). Stay tuned.

History

This effort started in October 2011 after some study and appreciation of Nakamoto's breakthrough work. We independently discovered proof-of-stake and worked on redesigning a significant portion of Nakamoto's protocol. The main goal of ppcoin is to validate that energy efficiency is achievable with cryptocurrency. We hope our work would contribute to the advancement of the revolutionary new field.

Update (2012-08-16):

We are busy preparing the final build of the release. Official block chain is tentatively scheduled to start at SUNDAY 2012-08-19 18:00:00 UTC

Disclaimer: This is experimental beta software so play at your own risk. We reserve the right to restart block chain should severe flaws require such actions but we will try our best to avoid such scenario as much as possible.

Release builds will be available for download a few hours before the scheduled block chain start time. Source code and design paper will be available around the same time or earlier.

I am happy to announce that project ppcoin is now close to beta quality and will be released to public soon.

What are we announcing?

- First implementation of hybrid proof-of-work/proof-of-stake - Long term energy non-dependence (meaning if hashrate drops network is still protected) - Long term energy efficiency (assuming the continuation of Moore's law) - Proof-of-work mint rate is a function of difficulty (every 16x in difficulty mint rate is halved) - Proof-of-stake mint rate is less than 1% annually - Centrally broadcasted checkpoint for transaction settlement and defend against 51% attacks

- No premine - No tax - Open source - Same license term as Bitcoin to help advancing cryptocurrency technology

Schedule

- Beta release is tentatively scheduled for Aug 19, 2012. In the first release only command-line client is available (ppcoind). Stay tuned.

History

This effort started in October 2011 after some study and appreciation of Nakamoto's breakthrough work. We independently discovered proof-of-stake and worked on redesigning a significant portion of Nakamoto's protocol. The main goal of ppcoin is to validate that energy efficiency is achievable with cryptocurrency. We hope our work would contribute to the advancement of the revolutionary new field.

Mining is compatible with Bitcoin mining, but not merge-minable with Bitcoin.

Regarding checkpointing I know it's going to be controversial so I'll try to explain here:

- Centrally broadcasted checkpointing is not considered part of the immutable core of the protocol, but is needed to make commerce practical as proof-of-stake is somewhat weaker in protection against double spending. Initially it is enforced strongly to protect against malicious powerful miners during the early mining stage. In the future it may be relaxed or replaced with a decentralized version should such algorithm become ready.

- We consider the checkpointing mechanism a more centralized version of Bitcoin's checkpointing, but not as centralized as SolidCoin's trust node. This is because if the node generating checkpoints fails or disconnects, block chain still continues, but in SolidCoin's case if trust node fails block chain would stop, and that's why they need 10 of those I think. So checkpoints are a centralized form of protection of the block chain, but that doesn't invalidate the purpose of miners/minters as block chain can run on it's own without the protection of checkpoints, albeit with some higher risk.

- We did fret over this issue during our development, but this is currently the best practical solution we deem ready for release. I am sure we will revisit this topic in the future.

Mining is compatible with Bitcoin mining, but not merge-minable with Bitcoin.

Regarding checkpointing I know it's going to be controversial so I'll try to explain here:

- Centrally broadcasted checkpointing is not considered part of the immutable core of the protocol, but is needed to make commerce practical as proof-of-stake is somewhat weaker in protection against double spending. Initially it is enforced strongly to protect against malicious powerful miners during the early mining stage. In the future it may be relaxed or replaced with a decentralized version should such algorithm become ready.

- We consider the checkpointing mechanism a more centralized version of Bitcoin's checkpointing, but not as centralized as SolidCoin's trust node. This is because if the node generating checkpoints fails or disconnects, block chain still continues, but in SolidCoin's case if trust node fails block chain would stop, and that's why they need 10 of those I think. So checkpoints are a centralized form of protection of the block chain, but that doesn't invalidate the purpose of miners/minters as block chain can run on it's own without the protection of checkpoints, albeit with some higher risk.

- We did fret over this issue during our development, but this is currently the best practical solution we deem ready for release. I am sure we will revisit this topic in the future.

11 Posts and you have almost been a year on this? I know I sound like an ass when I say this but seriously. You think BBQ Coin II: Judgement Day is really worth it? You might stand to make more money by putting this effort into an existing project. No one is asking the right questions here. Probably because like i said BBQ2 J-Day.

smoothie: proof-of-work uses same hash of Bitcoin, sha256 times 2. You should be able to use most Bitcoin mining tools although we have only tested with cgminer.

Etlase2: there is good reason that checkpoint is still needed in the first place, even when network is matured and one does not care about practical impact of large reorganization of the block chain. Once more detail of the design is made public later this week I can discuss more about that. Although for practical reasons we favor having a more limited time checkpoint such as less than one day behind the latest block to guarantee the safety of large transfers, at the very least during the early stage of the network.

We are busy preparing the final build of the release. Official block chain is tentatively scheduled to start at SUNDAY 2012-08-19 18:00:00 UTC

Disclaimer: This is experimental beta software so play at your own risk. We reserve the right to restart block chain should severe flaws require such actions but we will try our best to avoid such scenario as much as possible.

Release builds will be available for download a few hours before the scheduled block chain start time. Source code and design paper will be available around the same time or earlier.

First, what Syke said. Master-checkpoints are too similar to Soiledcoin's "cop nodes", and much like soiledcoin's cop nodes could trivially be used to rollback/freeze a TX a certain government's lackeys dislike, should said lackeys grab the dev by the cojones (which is so much easier when one of the devs has provided what seems to be his IRL name in the whitepaper)

Second, I'm no analyst but this

Quote from: whitepaper

he protocol for determining which competing block chain wins as main chain has been switched over to use consumed coin age.

Seems like a really bad move.

With bitcoin, you could use Finney attacks to take candies from babies who didn't wait for 2-5 confirms, and you needed a large pile of expensive equipment and electricity to do so.

With this design, you can take candies from babies who don't want to wait for "central checkpoint" message to "immortalize" their TX with but a pile of old coins.And then you just wait for your pile of coins to "age again" and take the candy from another baby.RINSEREPEAT

And the only way the baby can counter that is waiting for the kind central checkpoint. Which makes one wonder just how often will it happen.

Third, "continuous" adjustment of not one, but two targets seems like an extremely......bold...... move.

I mean, if continuous adjustment is such a wonderful idea, why didn't bitcoin devs switch to continuous adjust already?

As I understand it, you are not distributing txn fees to proof-of-stake 'miners'. Instead, you are destroying txn fees. Is that right?

I am concerned that proof-of-stake miners may fail to include txns in the blockchain, since inclusion does not benefit them.

Also, as I understand it, you can contribute stake without necessarily submitting significant work to accompany it. There are two issues with this:

1) It make double-spend attacks easier because they no longer have meaningful hardware and electricity requirements.2) Stake-owners might create alternate histories. i.e. Say I utilize aged coins at block t to mine a block. At block t-1, my aged coins still exist and can be used to mine another block. If I have nasty inclinations, I could utilize my aged coins multiple times and create several different branches at block t. Subsequent miners would not be able to easily distinguish which one of these branches is the "correct" fork and thus add to them all.

If you require significant work to accompany stake (e.g. by making the proof-of-work difficulty target a decreasing function of the aged coin stake accompanying the work), then you could avoid problem 2 entirely. I suspect that you could also substantially alleviate problem 1 as well. I believe that incorporating a significant proof-of-work submission would substantially increase the number of aged coins you need to successfully carry out a double spend (fixing the probability of success and the number of blocks you are trying to roll back).

I hope that you will look for ways to address double-spends without relying on the stop-gap measure of checkpoints. Checkpointing is quite unpopular. Incorporating a larger proof-of-work component and requiring people to wait longer to have confidence in the irreversibility of high-value sends might be a better solution.

Anyways, delightful to see a beta and I hope people will play around with attacking it.